Plug gap for non stock plug?

.024 will give you reliable ignition for a long period without straining the ign system.

Use the stock gap. Your ign system is designed for a certain amount of resistance/spark gap. Using a larger gap would tax the ign system and in the end produce a weak/possibly intermitant spark. By the way, you can save 1/2 the price of the IEX plug and use a BR8EG. The IEX plug will not resist fouling any better and just uses a different material to transmit the spark. You could also get away with using a BR8ES which is even cheaper! I always used the BR8EG and never had a failure (I also kept a close eye on maintenace and jetting).